NEW DELHI (Metro Rail News): Good quality concrete is one of the key objectives for various metro rail elements like piles, pile caps, piers/pillars, pre-cast girders etc. It is a product of cement, sand, aggregate (10mm and 20mm), micro silica/fly ash and water. The strength of reinforced concrete reflects the strength of all the structures in a metro project. Casting concrete structures at the casting yard ensures better quality management where factory-like quality systems are provided compared to cast in situ. Priority is to ensure it provides a quality product with utmost precision, which is a significant concern for the safety and durability of concrete structures in any Mass Rapid Transit System (MRTS) like Patna Metro.
As metro structures have a design life of more than 100 years, various tests are being done on fresh and hardened concrete to ascertain the quality. These tests are performed in the quality lab made at the casting yard and independent third-party labs.
Importance of casting yard and batching plant in ensuring suitable quality structures:Â
Metro projects are primarily built in busy cities. Hence, most of the construction work takes place at the casting yard to provide premium-quality structures and avoid any inconvenience to the public. For underground stations, 40% of the concrete casting takes place at the casting yard, and the figure goes up to 60% for elevated stretch. However, 100% of concrete mixing and making is done at the batching plant, usually at the casting yard’s premises. This amplifies the role of the casting yard and batching plant in the Patna Metro project immensely. Currently, three casting yards are in work; two are near LCT ghat and one near Fatuha.
Quality Supervision
Fresh and hardened concrete is tested in the labs to ensure quality. Every casting yard and batching plant has its quality lab to look after the strength and calibre of the product. Separate tests for all components, such as impact value, crushing value, water absorption, silt content etc., are conducted. Fresh concrete sample cubes are cast and kept in water for 28 days to test their strength and durability. After completing all the tests mentioned above, the pre-cast structures are erected at the site.
Environmental Supervision
The focus on preventing environmental degradation while casting pre-cast structures is paramount. Beton wash is used to recycle waste concrete from concrete-carrying mixers/vehicles. This waste concrete is further used for making paver blocks, kerb stones, footpath restoration and other site development works. Dust suppressors and dust arrestors prevent air pollution near batching plants. A wheel wash facility is also used at the exit point of the casting yard to wash the wheels of every construction vehicle that goes out. This prevents mud and soil from exiting the site along with the wheels of the vehicles. Other activities like topsoil conservation, translocation of trees, bio-toilet, etc., are also followed religiously.Â
DMRCÂ follows the abovementioned practices rigorously and does not compromise on these parameters that the organisation has followed for the last 25 years, yet ensures timely project completion within the planned time frame.
